158 BRITISH TYEOGLYPHID^]. 



when the cover was removed for the cell to be 

 examined during which time it was watched, more 

 larvae and young nymphs of Tgroglyphus soon appeared, 

 being bred from the eggs which previous adults had 

 laid, and older nymphs resulting from many of 

 the Hypopi undergoing ecdysis, were also found ; 

 but these things occurred gradually, the Hypopi 

 did not vanish suddenly, nor were fresh adults 

 to be found until they had grown. The experiment of 

 allowing the cell to get dry, or partially dry, was 

 repeated several times, but always with the same 

 results. It appeared evident, therefore, that desicca- 

 tion or other unfavourable circumstances would not 

 cause Tyroglyphus nymphs to change into Hypopi more 

 rapidly than they would otherwise have done. 



In the spring of 1882 I resumed the inquiry ; I 

 stayed at a farm where an old-fashioned chaff-house 

 adjoined the stable; this was not kept in the well- 

 swept condition of modern stables, chaff and debris of 

 fodder remained in a pile on the damp brick floor, and 

 the conditions were extremely favourable to Tyroglyphus 

 life. Warmth, moisture, and food in abundance were 

 there, and the chaff teemed with life. Tyroglyphidse * 

 swarmed, numbers of Gramasidas were preying upon 

 them ; minute Diptera and their larvas, Myriapoda, etc., 

 were abundant, but Hypopi also were in immense pro- 

 fusion, and continued to be so, and to attach themselves 

 to every living insect or Gamasid which came into the 

 chaff. The hotbed for cucumbers at the same place, 

 which was made of stable manure, presented equally 

 favourable conditions for Tyroglypki, quantities of 

 which throve there ; it swarmed with hypopi, which 

 covered every small dipterous insect which emerged 

 from the hotbed. It was therefore evident that the 

 most favourable conditions did not prevent Tyroglyphus 

 turning into Hypopus. 



* Principally Tyroglyphus mycophagus, Histiostoma rostro-serratum, 

 and Ahurobius farinse ; but the last-named species is not known to 

 have any bypopial stage. 



